Using crushed shale samples to obtain pore information from the gas adsorption experiments is a widely used method. Previous studies have evaluated the impact of the particle size on the pore size distribution, but potential pore shape damage during the crushing process has not been thoroughly investigated. In this paper, we crushed and sieved the same shale samples into five different particle sizes and studied their pore structures using nitrogen adsorption. The results demonstrate that, as the particle size decreases, the shape of the hysteresis loop changes from H2 type (ink-bottle pore shape) to H3 type (slit pore shape). The hysteresis index decreases as the particle size decreases, indicating potential damage of the ink-bottle pores during crushing. As the particle size becomes smaller, the pore complexity first decreases and then remains steady. We, therefore, conclude that crushing shale samples into smaller particle sizes could damage the ink-bottle-shaped pores, which needs to be considered in sample preparation protocols for the gas adsorption analysis.

The elements of Bakken Petroleum System consist of two source rocks with high underlying burial depths for significant hydrocarbon generation. However, this deep hydrocarbon generation process is dependent on its kinetic properties, thermal maturity, and geochemical properties. The statistical compensation effect is a complicating factor in the kinetic analyses of the Bakken Formation. In this study, we experimentally determined the kinetics of the Bakken formation source beds, observed the presence of the residual compensation effect, and numerically established a correlation between the kinetic parameters, thermal maturity indices ( T max ), and the vitrinite reflectance (VR o ) and bitumen reflectance (BR o ). First, we conducted source rock analysis to determine kinetic properties and the organic geochemical assays of reactive kerogen in the Bakken source beds. Finally, we incorporated previous established studies to generate numerical correlation for T max in terms of VR o and BR o reflectance. Our kinetic results show evidence of the residual compensation effect in the Bakken Formation when samples are repeatedly analyzed. The simultaneous linear expression of the residual compensation effect and the regression analysis of the solutions to the Kissinger equation for heating rate, yielded a kinetic parameter solution that correlates with T max . Furthermore, recalculated T max values established a correlation between the kinetic parameters, T max , VR o , and BR o . The application of state-of-the-art numerical correlations to measure subsurface kinetics, source rock richness, and burial-depth temperatures will enhance the accuracy of reservoir exploration and hydrocarbon production within the Bakken Formation.

Biogenic gas shales, predominantly microbial in origin, form an important class of organicrich shale reservoirs with a significant economic potential. Yet large gaps remain in the understanding of their gas generation, storage, and transport mechanisms, as previous studies have been largely focused on mature thermogenic shale reservoirs. In this study, the pore structure of 18 Antrim Shale samples was characterized using gas adsorption (CO 2 and N 2 ). The results show that most of the Antrim Shale samples are rich in organic matter content (0.58 wt.% to 14.15 wt.%), with highest values found in the Lachine and Norwood members. Samples from the Paxton Member, characterized by lower organic content, have smaller micropore surface area and micropore volume but larger meso-macro pore surface area and volume. The deconvolution results of the pore size distribution from the N 2 adsorption indicate that all of the tested Antrim Shale samples have similar pore groups. Organic matter in the Antrim Shale hosts micro pores instead of meso-macro pores, while clay minerals host both micro and meso-macro pores. Mineralrelated pores play a primary role in the total porosity. The biogenic Antrim Shale, therefore, has different pore structures from other well-studied thermogenic gas shales worldwide. KEY WORDS: gas adsorption, Antrim Shale, biogenic shale, organic matter. INTRODUCTIONThe recent boom in hydrocarbon production from unconventional reservoirs has led to significant advances in understanding of the microstructure and petrophysical properties of organic-rich shales. However, most of the shale gas formations being developed and extensively studied in the United States are thermogenic systems, such as Bakken Shale (in the Williston Basin), Barnett Shale (in the Fort Worth Basin), Marcellus Shale (in the Appalachian Basin), and Woodford Shale (in the Arkoma Basin) (

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